The present invention relates to an accentuator plate in the soundboard of a stringed musical instrument, and more particularly it relates to a vibrating soundboard accentuator plate for improving the tonal qualities of a stringed musical instrument.
Stringed musical instruments have been known, played and enjoyed since antiquity. Such acoustical instruments are characterized by a body, usually hollow, a neck extending from the body in one direction, and one or more strings suspended under controllable tension from a bridge mechanically coupled to a soundboard of the body to a hub at the distant end of the neck. As the string is vibrated by plucking, strumming, bowing, etc., the vibrations thereby induced in the string are transmitted by the bridge to the soundboard. The hollow body collects and directs the sounds in a forward direction, usually through openings, such as the central port in front of the bridge of an acoustical guitar.
While stringed musical instruments have been refined and improved over the years, they have still been characterized by some drawbacks. Non-linear frequency response and flat tonal qualities have characterized all but the most expensive of instruments. Unacceptably low output amplitudes for the lower notes of the instrument's voice and lack of sustain are additional drawbacks of the instruments of the prior art. Thus, a need has arisen for an improvement in stringed musical instruments which increases the volume, which lengthens the sustain qualities, which accentuates the low notes or bass frequencies, which improves the sensation of stronger upper partials and which endows the instrument with a more brilliant and even "shimmering" sound quality across the entire range thereof.
A number of approaches were taken by previous workers. One is depicted in U.S. Pat. No. 4,031,798 to Sidner, issued June 28, 1977. Therein, the soundboard was made of separately joined circumferential sectors or wedges which converged upon the location of the bridge. Sidner correctly recognized that the conventional soundboard contributed its own resonances and mechanical vibratory characteristics to the instrument to "color" its tonal qualities. Sidner's proposed solution was to construct the soundboard of "radially/circumferentially anistrophic sheets" which meant sheets having more uniform sound transmitting properties than the conventional wooden soundboards having longitudinal grain. The readily apparent drawback of the Sidner approach is the difficulty of constructing the radial wedges and the plurality of concentric ring braces.
Another prior approach is found in U.S. Pat. No. 3,233,495 to Bernardi, issued Feb. 8, 1966. Therein, a removable resonator attachment fitted over the bridge and strings with the hope of improving tonal qualities of the stringed instrument. That approach was unsatisfactory because the forearm of the player would come into contact with the resonator plate during playing and absorb sounds that would otherwise have been radiated. In addition, as the resonator plate was removable and touched the soundboard only through a gasket, very little, if any alteration of the basic tonal qualities of the soundboard were achieved. A similar approach was described in U.S. Pat. No. 1,617,454 to Monaco, issued Feb. 15, 1927. Therein, a resonator plate covered the upper end of the guitar body, but it required special bracing and a tongued brace which traversed the resonator. Complex construction, and interference with the fingerboard were apparent drawbacks in that approach.
A further prior approach is discussed in U.S. Pat. No. 4,068,553 to Dopyera, issued Jan. 17, 1978. Therein, guitars marketed under the trademark "DOBRO" were improved upon by the addition of a second "speaker cone like" vibrator mechanically linked directly to the bridge of the instrument. Both resonators were synchronized to "pump" together to achieve a tonal quality said to be desirable for "bluegrass" style music. One drawback of the so-called "DOBRO" approach is the mechanical complexity such instruments require.
Other prior art approaches included other forms of resonators mechanically linked to the bridge of a stringed instrument. For example, in U.S. Pat. No. 3,353,433 to Webster, issued Nov. 21, 1967, a tuning fork depending downwardly into the soundbox was attached at its common end to a "floating" bridge. In U.S. Pat. No. 81,012 to Schleicher, issued Aug. 11, 1868, an angled tongue was mounted inside the soundbox from the bridge to a lower point opposite the sound opening. Exterior longitudinal bracing strips on the backside of the soundboard was said to improve tonal qualities in a stringed musical instrument in U.S. Pat. No. 4,104,945 to Bolin, issued Aug. 8, 1978. A moving coil linear transducer was provided within the soundbox to facilitate electronic amplification.
Shaping the backside of the soundboard into a paraboloid reflector was thought to improve tonal quality in a guitar in U.S. Pat. No. 4,178,827 to Mallory. Special bracing and fastening of the bridge thereto was also thought to play a part in that invention. A less radically curved backside was depicted in U.S. Pat. No. 3,474,697 to Kaman, issued Oct. 28, 1969. The same inventor also emphasized special interior bracing patterns to achieve superior tonal qualities in a guitar in U.S. Pat. No. 3,656,395, issued Apr. 18, 1972. All of these prior art approaches required special construction techniques for the intrument and did not readily lend themselves to conversion of existing instruments.